Amplitude-shift keying (ASK) modulation is a form of modulation that represents digital data (binary one or zero) as variations in an amplitude of a carrier wave. One form of an ASK modulator operates as one single switch (on-off keying), using the presence of the carrier wave to indicate a binary one and its absence to indicate a binary zero. However, having a simple configuration, on-off keying presents no flexibility in terms of modulation depth.
Flexible modulation depths can be realized by distributing the carrier wave power control to multiple switches. The switches are driven by a clock signal and therefore introduce a clock component in an output spectrum. However, the clock component is very close to a central frequency so that the clock component can't be removed effectively, thereby causing inter-channel interference.
Mixers such as Gilbert mixers are not subject to such disadvantages but are still deficient due to nonlinearity.
Therefore, a new modulator, mixer and method for ASK modulation are required.